Additivation of essentially amorphous cellulose nanofibrils with carboxyl cellulose with a high degree of substitution

ABSTRACT

The present invention relates to compositions comprising essentially amorphous cellulose nanofibrils, at least one additive chosen from carboxycellulose with a degree of substitution of more than 0.95, a natural polysaccharide, a polyol, and optionally at least one co-additive, the content of additive and of optional co-additive being less than or equal to 30% by weight relative to the weight of nanofibrils and of additive and of optional co-additive. Similarly, a subject of the invention is a process for preparing such compositions, which consists in adding the additive and the optional co-additive to a suspension of essentially amorphous nanofibrils, and then in drying the suspension thus supplemented. The compositions obtained are redily redispersable and conserve their initial rheological properties.

This application is a 317 of PCT/FR97/01291 field July 1997.

The present invention relates to compositions comprising essentiallyamorphous cellulose nanofibrils, at least one additive chosen fromcarboxycellulose with a degree of substitution of more than 0.95, anatural polysaccharide, a polyol and optionally at least oneco-additive, as well as to a process for their preparation.

The invention relates to the suspensions obtained from suchcompositions.

Cellulose microfibrils and nanofibrils are well-known compounds whichare used as additives for modifying the texture of media into which theyare introduced. In the case of fluid media, they modify their viscosityor even their rheological profile.

However, there is a problem with cellulose microfibrils and nanofibrils,which is that they are obtained in the form of an aqueous suspensionwhose solids content is relatively low, from about 1 to about 5% byweight approximately. The development of these products in such a formis thus not economically viable, either in terms of storage ortransportation, for example. It has thus been considered, naturally, topresent them in a dry form. Unfortunately, when the cellulosemicrofibril or nanofibril suspensions are dried, very strong hydrogenbonds are created between the fibrils which make it necessary to usevery high-shear means to redisperse these fibrils, when it is possibleto resuspend them.

Attempts have been made to propose solutions to the problem of dryingcellulose microfibrils. Thus, additives have been introduced during thepreparation of microfibril suspensions, and more particularly at thetime of the homogenization.

For example, U.S. Pat. No. 4,481,076 proposes drying the cellulosemicrofibrils obtained from wood pulp in the presence of additive. Thecontents which are most favourable for good redispersion after drying,and thus for a good viscosity level of the suspension, are from about 50to about 100% by weight relative to the dry microfibrils. As may beobserved, the amounts of additives introduced are very large. Moreover,these methods are not entirely satisfactory, even though it is possible,in principle, to redisperse these dried microfibrils, since the meansused for the redispersion are still very high-shear.

International patent application WO 95/02966 describes thesupplementation of microcrystalline cellulose with xanthan gum orcarboxymethylcellulose, with contents of less than 33% by weightrelative to the weight of microcrystalline cellulose. However, extremelyhigh-shear conditions are used to suspend the dried cellulose, sincethey are carried out under the standard conditions for stirringformulations intended for applications in the food sector. The driedmicrofibrils can thus not be considered as easily redispersible.

The teaching provided by the prior art regarding the redispersion ofmicrocrystalline cellulose microfibrils, and in particular thoseobtained from wood pulp, cannot be transposed to cellulose nanofibrils,obtained from cells with primary walls.

Firstly, the cellulose microfibrils obtained from wood are derived fromsecondary walls. This means that they have a greater than 70% degree ofcrystallinity. During the step of homogenization of the microfibrilsobtained from wood, rather than observing a disentangling of the fibres,as is the case during the step of homogenization of the cellulosenanofibrils obtained from primary walls, these fibrils are found tobreak. Consequently, the cellulose microfibrils obtained from secondarywalls do not have the characteristics of amorphous fibrils, but, rather,have the characteristics of microcrystalline microfibrils.

Moreover, the morphologies of the microfibrils and nanofibrils aredifferent. In point of fact, the microcrystalline microfibrils, forexample obtained from cellulose with secondary walls, such as wood pulp,are conventionally in the form of aggregates from a few tens ofnanometres to a few micrometres, consisting of elementary fibrils, whichcannot be disentangled during the homogenization step. As regards thecellulose nanofibrils obtained from cells with primary walls, they havea diameter of not more than a few nanometres and have the appearance offilaments.

It is relatively well established that the difficulty in redispersingcellulose microfibrils or nanofibrils is associated with the existenceof numerous hydrogen bonds between the fibrils, which are created duringdrying. Now, the number of hydrogen bonds per weight unit of celluloseis directly associated with the morphology of the said microfibrils ornanofibrils, and, more specifically, is proportional to their specificsurface; the greater the specific surface, the larger the number ofhydrogen bonds per weight unit of cellulose. Given the particularmorphology of the cellulose nanofibrils obtained from cells with primarywalls, the specific surface of these nanofibrils is much higher thanthat of the microfibrils. A person skilled in the art would thuslogically expect to encounter greater difficulties in redispersingcellulose nanofibrils.

Thus, given the state of the art presented above, it could be envisagedthat larger amounts of additive than those used for the microfibrilswould be necessary in order to obtain good redispersion of the driednanofibrils.

However, the present invention has shown, against all expectations, thatrelatively low amounts of additive are sufficient to allow goodredispersion of the dried nanofibrils, and without it being necessary touse extremely high-shear conditions. In addition, it has been found,surprisingly, that amounts of the order of those recommended in theprior art have considerable drawbacks as regards conserving therheological properties of the nanofibrils.

This arises from the difference in behaviour between the crystallinemicrofibrils, for example the cellulose microfibrils obtained fromsecondary walls, and the nanofibrils obtained from cells with primarywalls.

The reason for this is that the non-supplemented microcrystallinemicrofibrils are not dispersible in aqueous medium; they separate out bysettling as soon as the stirring is stopped, even when very high-shearstirring means are used. Furthermore, they do not give shear-thinningrheological properties.

On the other hand, the nanofibrils obtained from primary walls are of anature which is dispersible in aqueous medium. In addition, they give aquite specific rheological profile, of shear-thinning type, to themedium into which they are introduced.

Now, in general, drying adversely affects not only the capacity forredispersion of the dried nanofibrils and their viscosity, but alsotheir rheological profile. Thus, large amounts of additives of the typeusually used to redisperse microcrystalline microfibrils, such as thoseobtained from wood, i.e. as much additive as microfibrils, do not givegood results as regards the shear-thinning rheological profile of thecellulose nanofibrils obtained from primary walls: the profile becomesmore Newtonian, i.e. less shear-thinning.

As may be observed, the consequences of drying essentially amorphouscellulose nanofibrils in terms of the redispersion of these fibrils andtheir rheological properties (viscosity at low and high shear,rheological profile) cannot be solved in a satisfactory manner based onthe knowledge obtained from the supplementation of microcrystallinemicrofibrils, for example of microfibrils obtained from cells withsecondary walls.

The present invention thus provides a simple and effective solution tothese problems.

These aims and others are achieved by the present invention, a firstsubject of which is a composition comprising essentially amorphouscellulose nanofibrils, at least one additive chosen fromcarboxycellulose with a degree of substitution of more than 0.95, anatural polysaccharide, a polyol and optionally at least oneco-additive, the content of additive and of optional co-additive beingless than or equal to 30% by weight relative to the weight ofnanofibrils and of additive and optional co-additive.

Another subject of the present invention consists of a process forpreparing a composition, in which cellulose nanofibrils are preparedfrom cellulosic pulp by carrying out at least one extraction, optionallyfollowed by at least one step of bleaching the pulp thus treated, afterwhich the resulting pulp is separated out and a homogenization step iscarried out in at least one cycle, the characteristic of the processbeing that the following steps are carried out:

at least some of the additive and optionally co-additive(s) are added tothe nanofibril suspension which has optionally undergone at least onehomogenization cycle,

a step of drying the suspension thus supplemented is carried out.

A third subject of the invention relates to a suspension comprisingcellulose nanofibrils, which is obtained by redispersing the compositionaccording to the invention.

The present invention makes it possible simultaneously to propose aprocess for drying essentially amorphous nanofibrils in the presence ofadditives, as well as compositions which are dried such that they arereadily redispersible, while at the same time retaining the specificrheological properties of the initial non-dried suspensions. Thus, thesuspensions according to the invention, obtained after redispersing thecompositions, have a good level of viscosity at a low shear gradient, aswell as a rheological profile of shear-thinning type.

In addition, the means used to redisperse the dried compositionsaccording to the invention are considerably less shearing than thoseusually used to redisperse dried microfibrils obtained from wood or fromother secondary walls.

Other characteristics and advantages of the present invention willemerge more clearly on reading the description and the examples whichfollow.

As has been mentioned previously, the subject of the present inventionis the supplementation of essentially amorphous cellulose nanofibrils.

The term “essentially amorphous” is intended to refer to nanofibrilswhose degree of crystallinity is less than or equal to 50%. According toa specific variant of the present invention, the degree of crystallinityis between 15% and 50%. Preferably, the degree of crystallinity is lessthan 50%.

The cellulose nanofibrils treated according to the present invention areobtained from cells preferably consisting of at least about 80% primarywalls. Preferably, the amount of primary walls is at least 85% byweight.

Such characteristics are present in particular in parenchymal cells.Sugar beet pulp, citrus fruits such as lemons, oranges and grapefruit,and most fruit and vegetables are examples of parenchyma.

Moreover, the nanofibrils forming part of the compositions according tothe invention are, according to a particularly advantageous variant,charged at the surface with carboxylic acids and with acidicpolysaccharides, alone or as a mixture.

The term “carboxylic acids” is intended to refer to simple carboxylicacids, as well as salts thereof. These acids are preferably chosen fromuronic acids. More particularly, the said uronic acids are moreparticularly galacturonic acid and glucuronic acid.

As acidic polysaccharides, mention may be made of pectins, which aremore particularly polygalacturonic acids. These acidic polysaccharidescan be present as a mixture with hemicelluloses.

The cellulose nanofibrils also have a cross-section of between about 2and about 10 nm. More particularly, the nanofibril cross-section isbetween about 2 and about 4 nm.

According to a particularly advantageous embodiment of the presentinvention, the nanofibrils forming part of the compositions according tothe invention are obtained by using the treatment which will bedescribed below. More particularly, this treatment is carried out on thepulp of vegetables with primary walls, such as, for example, beetrootpulp, after it has undergone a preliminary step of extraction of thesucrose, according to the methods known in the art.

Thus, the process comprises the following steps:

(a) first acidic or basic extraction, after which a first solid residueis recovered,

(b) optionally, second extraction, carried out under alkalineconditions, of the first solid residue, after which a second solidresidue is recovered,

(c) washing of the first or second solid residue,

(d) optionally, bleaching of the washed residue,

(e) dilution of the third solid residue obtained after step (d) so as toobtain a solids content of between 2 and 10% by weight,

(f) homogenization of the dilute suspension.

In step (a), the term “pulp” is intended to refer to wet, dehydratedpulp stored by ensilage or partially depectinized.

The extraction step (a) can be carried out in acidic medium or in basicmedium.

For an acidic extraction, the pulp is suspended in an aqueous solutionfor a few minutes so as to homogenize the acidified suspension at a pHof between 1 and 3, preferably between 1.5 and 2.5.

This operation is carried out with a concentrated solution of an acidsuch as hydrochloric acid or sulphuric acid.

This step may be advantageous for removing the calcium oxalate crystalswhich may be present in the pulp, and which, on account of their highlyabrasive nature, can cause difficulties in the homogenization step.

For a basic extraction, the pulp is added to an alkaline solution of abase, for example sodium hydroxide or potassium hydroxide, with aconcentration of less than 9% by weight, more particularly less than 6%by weight. Preferably, the concentration of the base is between 1 and 2%by weight.

A small amount of a water-soluble antioxidant, such as sodium sulphiteNa₂SO₃, may be added in order to limit the oxidation reactions of thecellulose.

Step (a) is generally carried out at a temperature of between about 60°C. and 100° C., preferably between about 70° C. and about 95° C.

The duration of step (a) is between about 1 hour and about 4 hours.

During step (a), partial hydrolysis takes place with release andsolubilization of most of the pectins and hemicelluloses, while at thesame time retaining the molecular mass of the cellulose.

The solid residue is recovered from the suspension obtained from step(a) by carrying out known methods. Thus, it is possible to separate thesolid residue by centrifugation, by filtration under vacuum or underpressure, with filter gauzes or filter presses, for example, or else byevaporation.

The first solid residue obtained is optionally subjected to a secondextraction step carried out under alkaline conditions.

A second extraction step, step (b), is carried out when the first stephas been carried out under acidic conditions. If the first extractionhas been carried out under alkaline conditions, the second step isoptional.

According to the process, this second extraction is carried out with abase preferably chosen from sodium hydroxide and potassium hydroxide,whose concentration is less than about 9% by weight, preferably betweenabout 1% and about 6% by weight.

The duration of the alkaline extraction step is between about 1 andabout 4 hours. It is preferably equal to about 2 hours.

After this second extraction, if it is carried out, a second solidresidue is recovered.

In step (c), the residue derived from step (a) or (b) is washedthoroughly with water in order to recover the residue of cellulosicmaterial.

The cellulosic material from step (c) is then optionally bleached, instep (d), according to the standard methods. For example, a treatmentwith sodium chlorite, with sodium hypochlorite or with hydrogen peroxidein a proportion of 5-20% relative to the amount of solids treated can becarried out.

Different concentrations of bleaching agent can be used, at temperaturesof between about 18° C. and about 80° C., preferably between about 50°C. and about 70° C.

The duration of this step (d) is between about 1 hour and about 4 hours,preferably between about 1 hour and about 2 hours.

A cellulosic material containing between 85 and 95% by weight ofcellulose is thus obtained.

After this bleaching step, it may be preferable to wash the cellulosethoroughly with water.

The resulting suspension, which has optionally been bleached, is thenrediluted in water in a proportion of 2 to 10% solids (step (e)), beforeundergoing a homogenization step (step (f)) comprising at least onecycle.

According to a first variant of the invention, the nanofibrils aresupplemented before undergoing the homogenization step.

According to a second variant of the invention, the cellulosenanofibrils are supplemented after they have undergone at least onehomogenization cycle.

The homogenization step corresponds to a mixing or blending operation orany operation of high mechanical shear, followed by one or more passagesof the cell suspension through an orifice of small diameter, subjectingthe suspension to a pressure drop of at least 20 MPa and to a high-speedshear action, followed by a high-speed deceleration impact.

The mixing or blending is carried out, for example, by passage(s)through the mixer or blender for a period ranging from a few minutes toabout an hour, in a machine such as a Waring Blendor fitted with afour-blade impeller or a pan mill mixer or any other type of blender,such as a colloidal mill.

The actual homogenization will advantageously be carried out in ahomogenizer such as a Manton Gaulin in which the suspension is subjectedto a shear action at high speed and high pressure in a narrow passageand against an impact ring. Mention may also be made of the MicroFluidizer, which is a homogenizer mainly consisting of a compressed-airmotor which creates very high pressures, an interaction chamber in whichthe homogenization operation takes place (elongational shear, impactsand cavitations) and a low-pressure chamber which allowsdepressurization of the dispersion.

The suspension is introduced into the homogenizer preferably afterpreheating to a temperature of between 40 and 120° C., preferablybetween 85 and 95° C.

The temperature of the homogenization operation is maintained between 95and 120° C., preferably above 100° C.

The suspension is subjected to pressures of between 20 and 100 MPa andpreferably above 50 MPa in the homogenizer.

Homogenization of the cellulosic suspension is obtained by a number ofpassages which can range between 1 and 20, preferably between 2 and 5,until a stable suspension is obtained.

The homogenization operation can advantageously be followed by a highmechanical shear operation, for example in a machine such as theSylverson Ultra Turrax.

It should be noted that this process has been described in Europeanpatent application EP 726,356 filed on Jul. 2, 1996, and reference maythus be made thereto if necessary. Example 20 of that text in particulargives a method for preparing a suspension of essentially amorphouscellulose nanofibrils.

The additives will now be described.

The first additive, or simply the additive, forming part of thecomposition according to the invention is chosen from carboxycellulose,in salt or acid form, with a degree of substitution of more than 0.95, anatural polysaccharide and a polyol.

The additives mentioned can be present alone or as mixtures.

According to a first embodiment, the additive of the compositionaccording to the invention consists of carboxycellulose with a specificdegree of substitution.

The cellulose used as additive is more particularlycarboxymethylcellulose. Cellulose is a polymer consisting of glucosemonomer units. The carboxyl group is introduced in a manner which isknown per se, by reacting chloroacetic acid with cellulose.

The degree of substitution corresponds to the number of carboxymethylgroups per glucose unit. The maximum theoretical degree is 3.

According to the invention, the degree of substitution ofcarboxymethylcellulose is therefore more than 0.95.

The degree of polymerization of the carboxycellulose used as nanofibriladditive, in accordance with the present invention, varies within a widerange. Thus, carboxymethylcelluloses of high masses (high degree ofpolymerization, high viscosity) or of low masses (low degree ofpolymerization, low viscosity) are suitable.

In the first category, mention may be made of celluloses whose viscosityis between about 9000 mPa.s, measured in an aqueous 1% solution(Brookfield, 30 rpm), and 250 mPa.s, measured in an aqueous 6% solution(Brookfield, 60 rpm).

In the second category, mention may be made of celluloses whoseviscosity is between about 250 mpa.s, measured in an aqueous 6% solution(Brookfield, 60 rpm), and 10 mpa.s, measured in an aqueous 6% solution(Brookfield, 60 rpm).

In the case of the first category, the carboxycellulose content is lessthan or equal to 30% by weight.

In the case of the second category, the carboxycellulose content is moreparticularly between 10 and 30% by weight.

The additive forming part of the composition according to the inventioncan also be a natural polysaccharide.

Thus, the polysaccharide can be of bacterial, animal or plant origin.

Polysaccharides are polymers comprising saccharide units.Polysaccharides in an anionic or nonionic form are preferably used.

Among the suitable anionic polysaccharides, mention may be made, withoutintending to be limited thereto, of xanthan gum, succinoglycans,carrageenans and alginates.

As nonionic polysaccharides, mention may be made, for example, ofgalactomannans, such as guar gum and carob gum. Starch and its nonionicderivatives are also suitable, as well as nonionic cellulosederivatives.

According to a specific embodiment of the invention, an anionicpolysaccharide, and more especially xanthan gum, is used as additive.

Among the suitable polyols, mention may be made most particularly ofpolyvinyl alcohol.

One preferred embodiment of the present invention consists of acomposition whose additive is the carboxycellulose as defined.

A second specific embodiment consists of an additive comprising apolysaccharide, preferably an anionic polysaccharide, optionallycombined with the abovementioned carboxycellulose.

The composition according to the invention can also comprise at leastone co-additive chosen from:

carboxycellulose with a degree of substitution of less than or equal to0.95, preferably carboxymethylcellulose,

saccharide monomers or oligomers,

compounds of formula (R¹R²N)COA, in which formula R¹ and R², which maybe identical or different, represent hydrogen or a C₁-C₁₀, preferablyC₁-C₅, alkyl radical, A represents hydrogen, a C₁-C₁₀, preferably C₁-C₅,alkyl radical or alternatively the group R′¹ R′²N with R′¹ and R′²,which may be identical or different, representing hydrogen or a C₁-C₁₀,preferably C₁-C₅, alkyl radical, cationic or amphoteric surfactants,

it being possible for these co-additives to be used alone or as amixture.

It should be noted that the observations made above regarding the natureand viscosities of the carboxycellulose, and more particularly thecarboxymethylcellulose with a high degree of substitution, remain validhere, with the exception of the degree of substitution.

Among the saccharide monomers or oligomers, mention may be made mostparticularly, and without intending to be limiting, of sorbitol, sucroseand fructose.

As regards the compounds of the type (R¹R²N)COA, it is preferred to usecompounds comprising two amide functions. Preferably, urea is used asco-additive.

Among the cationic surfactants, mention may be made of cationicquaternary ammonium derivatives such as, for example, cationicimidazoline derivatives, alkyltrimethylammonium,dialkyldimethylammonium, alkyldimethylbenzylammonium oralkyldimethylethylammonium halides and Quat esters.

As examples of suitable cationic compounds, mention may be made of theproducts sold by Rhône-Poulenc from the Rhodaquat range. It is alsopossible to use synthetic cationic polymers, known under the CTFAgeneric name of “Polyquaternium”, for example the polymers Mirapol A15®or Mirapol 550® from the company Rhône-Poulenc.

The surfactants forming part of the formulation according to theinvention can also be chosen from amphoteric surfactants. For example,mention may be made, without intending to be limiting, of alkylpolyamineamphoteric derivatives, alkylbetaines, alkyldimethylbetaines,alkylamidopropylbetaines, alkylamidopropyldimethylbetaines,alkyltrimethylsulphobetaines, imidazoline derivatives such as alkylamphoacetates, alkyl amphodiacetates, alkyl amphopropionates, alkylamphodipropionates, alkylsultaines or alkylamidopropylhydroxysultaines,and the condensation products of fatty acids and of proteinhydrolysates. it being possible for these compounds to be used alone oras a mixture.

The surfactants Mirapon® s Excel, Mirataine® CBS, Mirataine® CB,Mirataine H2CHA®, Ampholac 7T/X®, Ampholac 7C/X, the Miranol® range,Amphionic® SFB and Amphionic® XL may in particular be suitable forcarrying out the present invention.

When the compositions according to the invention comprise one or more ofthe abovementioned co-additives, their content is less than 30% byweight relative to the weight of nanofibrils and of additive and ofco-additive. Needless to say, the content of additive(s) and ofco-additive(s) is such that it is less than or equal to 30% relative tothe weight of nanofibrils, of additive(s) and of co-additive(s).

According to a first specific variant of the invention, the compositionscomprise at least one additive, as well as at least one co-additivechosen from carboxycellulose with a degree of substitution of less thanor equal to 0.95, saccharide monomers and oligomers or compounds offormula (R¹R²N)COA.

In the case of this first variant, the co-additive content is less than30% and preferably between 1 and 25% by weight relative to the weight ofnanofibrils and of additive and of co-additive.

According to a second specific variant of the invention, thecompositions comprise at least one additive and, as co-additive, atleast one compound chosen from cationic and amphoteric surfactants.

In the case of this second variant, the co-additive content is between 1and 10% by weight relative to the weight of nanofibrils and of additiveand of co-additive.

In each of the two variants, the content of additive is less than orequal to 30% by weight relative to the weight of nanofibrils and ofadditive and of co-additive.

In the case of redispersion additives such as carboxycellulose with ahigh degree of substitution (degree of substitution of more than 0.95)or of co-additives such as cellulose with a low degree of substitution(degree of substitution of less than or equal to 0.95), the higher itsconcentration, the more it lowers the shear-thinning nature of thecellulose nanofibrils by modifying their state of dispersion in thewater. Thus, in the case of carboxycellulose and for concentrations ofgreater than 30% by weight relative to the weight of nanofibrils and ofadditive and of co-additive, although the nanofibrils are redispersible,their rheological profile becomes more Newtonian, i.e. lessshear-thinning, which is undesirable.

In the case of the use of carboxycellulose with a high degree ofsubstitution, in comparison with a carboxycellulose with a low degree ofsubstitution, it has been observed that the carboxycellulose with a highdegree of substitution proves to be more effective in terms of itsredispersing power and its maintenance of the shear-thinning rheologicalprofile of the cellulose nanofibrils. Thus, for a similar mass ofcarboxycellulose, the required concentration of carboxycellulose with ahigh degree of substitution can advantageously be reduced relative to acarboxycellulose with a low degree of substitution.

Thus, the said content of additive and of optional co-additive can bechosen to be less than or equal to 25% by weight relative to the weightof nanofibrils and additive and of optional co-additive; this content ispreferably between 5% and 25% by weight relative to the same reference;thus, the cellulose nanofibrils redisperse easily and retain theirshear-thinning rheological properties.

It should be noted that the use of such co-additives described abovemakes it possible, in combination with carboxymethylcellulose, toreinforce the shear-thinning profile of the cellulose nanofibrils afterredispersion.

In addition, the compositions according to the invention have a solidscontent of at least 40% by weight. More particularly, the solids contentis at least 60% by weight and is preferably at least 70% by weight.

Advantageously, it has been noted that the rheological profile ofsuspensions dried until a solids content of this order is obtained isnot adversely affected.

The particle size of the composition according to the invention can varywithin a wide range. It is usually between 1 μm and a few millimetres.

The process for preparing the compositions will now be described ingreater detail.

The process according to the invention consists firstly in preparing thecellulose nanofibrils from appropriate cellulosic pulp, by carrying outa hydrolysis, optionally followed by at least one step of bleaching ofthe pulp thus treated. Everything which has been mentioned previously inthis respect remains valid and will not be repeated here.

The process for preparing the compositions according to the inventionconsists, in a first step, in adding at least some of the additive andoptionally co-additive(s) to the nanofibril suspension, which hasoptionally undergone at least one homogenization cycle. Next, in asecond step, a step of drying the suspension thus supplemented iscarried out.

According to a first advantageous variant of the present invention, theaddition of at least some of the additive and optionally co-additive(s)is carried out after the homogenization step.

One particularly suitable embodiment of the invention consists in addingat least some of the additive and optionally co-additive(s) to thesuspension after the homogenization step, after this suspension hasundergone at least one concentration step.

The concentration step(s) take place by filtration, centrifugation orevaporation of some of the water from the suspension. It is possible,for example, to use filters under vacuum or under pressure, sprayingtowers, ovens or microwave ovens.

It is thus possible to carry out a precipitation, for example in analcohol such as ethanol, isopropanol or any other similar alcohol tocarry out a process of separation by freezing-thawing, by dialysisagainst a hygroscopic solution in which the size of the molecules isgreater than the size of the pores in the membrane used.

These methods are cited merely as guides and cannot be considered as anexhaustive list.

According to this embodiment, the concentration operation can be carriedout until a solids content of about 35% by weight is obtained. Moreparticularly, the solids content is between 5 and 25% by weight.

The introduction of the additive and optionally co-additive(s) iscarried out in a manner which is known per se, i.e. by any means whichallows homogeneous introduction of a solution, a suspension or a powderto a suspension which tends to have the consistency of a paste. Forexample, mention may be made of blenders, extruders and mixers.

This operation can be carried out over a wide temperature range, moreparticularly between room temperature and 80° C. It may be advantageousto carry out the introduction at the temperature at which theconcentration took place. It should also be noted that temperatures fromabout 50 to about 80° C. can also facilitate the addition of theadditive, by decreasing its viscosity, for example.

A second embodiment of the process consists in adding at least some ofthe additive and optionally co-additive(s) to the suspension after thehomogenization step, before this suspension has undergone at least oneconcentration step.

In this latter case, the concentration step(s) which take place afterthe addition of additive and optionally of co-additive are carried outin the same way as indicated above.

If this first variant is carried out, a preferred embodiment of theinvention is to carry out the supplementation after the suspension hasundergone one or more concentration steps.

According to a second advantageous variant of the present invention, theaddition of at least some of the additive and optionally co-additive(s)is carried out before or during the homogenization step. When it isindicated that the supplementation takes place during the homogenizationstep, this means that the additive and optionally the co-additive(s) areintroduced when the pulp has undergone at least one cycle of thehomogenization step.

The supplementation takes place according to the methods indicated inthe context of the first variant.

Prior to the actual drying step, it may be advantageous to carry out ashaping of the suspension which has been concentrated as mentionedpreviously.

This shaping is carried out in a manner which is known to those skilledin the art. Mention may be made in particular, without, however,intending to be limited thereto, of extrusion and granulation.

The first is carried out in standard apparatus comprising any type ofdie, and the second can be carried out, for example, in drums orgranulators.

The drying is carried out by any means which is known to those skilledin the art, provided that this means makes it possible to have goodhomogeneity of the temperature of the shaped or unshaped suspension.

In this respect, mention may be made of evaporation in ovens on aconveyor belt, with or without induction, radiative or non-radiative,rotating ovens or fluidized beds, or in a freeze-dryer.

According to a particularly advantageous variant of the presentinvention, the drying step is carried out so as to maintain not lessthan 3% by weight of water relative to the weight of the solid obtained.More particularly, the weight of water maintained is between 10 and 30%by weight. Such an implementation makes it possible not to exceed thethreshold beyond which redispersion of the nanofibrils may no longer becomplete.

The drying advantageously takes place in air, although it may beenvisaged to carry it out under an inert gas, such as nitrogen.

It should also be noted that it is preferred to carry out the drying inan atmosphere whose degree of humidity is controlled so as to be able tomaintain the desired moisture content in the composition.

The drying temperature should limit any degradation of the carboxylicacids, of the acidic polysaccharides, of the hemicelluloses and/or ofthe additives and co-additives. It is more particularly between 30 and80° C., preferably between 30 and 60° C.

It should be noted that it would not constitute a departure from thecontext of the present invention to carry out a drying operation inseveral steps, some of which would use the means indicated above for theconcentration step.

After the drying step, the composition obtained can be blended.

If such a possibility is selected, the particle size of the powder isgenerally between 1 μm and a few millimetres, preferably between 30 μmand a few millimetres. Such a particle size makes it possible tofacilitate redispersion to a certain extent while at the same timelimiting handling problems.

Another subject of the present invention consists of a suspension ofcellulose nanofibrils which is obtained by redispersion of thesupplemented composition according to the invention in water or anyother medium.

Besides the fact that it can be obtained by redispersion of thecomposition according to the invention, the suspension according to theinvention has a rheological profile of shear-thinning type.

Moreover, it has a level of viscosity corresponding to at least 50%, fora shear rate of at least 1 s⁻¹, of the level of viscosity of a cellulosenanofibril suspension which has not undergone a drying step and whichdoes not comprise additives or co-additives.

A subject of the present invention is also the use of carboxycellulose,preferably carboxymethylcellulose, and optionally of co-additives, withessentially amorphous cellulose nanofibrils, with the aim of conservinga shear-thinning rheological profile for a suspension comprisingessentially amorphous cellulose nanofibrils which have undergone adrying step.

Everything which has been mentioned previously regarding the additives,co-additives and the other elements which make up the compositionaccording to the invention, as well as the preparation of the saidcomposition, remains valid and reference may be made thereto.

The compositions according to the invention and the suspensions obtainedby redispersion of these compositions can be used in many sectors inwhich it is desired to have a shear-thinning rheological profile. Thismay be the case for fluids used in petroleum exploitation, forformulations intended for the cosmetics, detergency or food sectors, oralternatively public works and construction.

Concrete but in no way limiting examples will now be given.

COMPARATIVE EXAMPLE 1

The Comparative Example is carried out in the absence of additive andco-additive.

The stock nanofibril dispersion used contains 2.3% by weight ofcellulose nanofibrils, supplied by Génèrale Sucriére, and isprehomogenized with an Ultra-Turrax machine at 14,000 rpm (1 min per 100g of dispersion).

This non-dried stock dispersion is then diluted to 0.3% by weight ofcellulose nanofibrils in distilled water using the Ultra-Turrax machineat 8000 rpm for 1 min. This constitutes the control solution.

The same stock dispersion is concentrated to a solids content of 40%using a filter press. The solid obtained is then redispersed to 0.3% byweight of cellulose nanofibrils in distilled water. The stirring iscarried out using the Ultra-Turrax machine at 8000 rpm for 1 min.Mixture 1 is thus obtained.

Flow rheology is carried out after 24 hours on a RFS 8400 rheometer inCouette geometry (scanning in shear gradient between 1 and 100 s⁻¹).

The results are summarized in Table I.

TABLE 1 Shear gradient Viscosity (Pa.s) Viscosity (Pa.s) (s⁻¹) ControlMixture 1 1.27 3.0 2.0 × 10⁻¹ 2.01 1.3 9.6 × 10⁻² 5.05 4.3 × 10⁻¹ 4.2 ×10⁻² 12.7 1.6 × 10⁻¹ 2.3 × 10⁻² 20.1 9.9 × 10⁻² 1.8 × 10⁻² 50.5 3.2 ×10⁻² 8.8 × 10⁻³ 80.0 1.6 × 10⁻² 6.4 × 10⁻³

In mixture 1, it is observed that the decantation volume (thesupernatant) reaches 10% after standing for 4 hours and exceeds 15%after standing for 24 hours, whereas the control remains stable.

Furthermore, the recovered viscosity, after concentration without anadditive and redispersion, is only 7% of the initial viscosity for ashear gradient of greater than or equal to 1 s⁻¹.

The Comparative Example shows that in the absence of additive such ascarboxymethylcellulose with a high degree of substitution, drying of thecellulose nanofibrils followed by redispersion with a high-shear machine(Ultra-Turrax) leads to an unstable dispersion which loses 93% of itsinitial viscosity for a shear gradient of greater than or equal to 1s⁻¹.

COMPARATIVE EXAMPLE 2

The aim of this example is to show the different behaviour ofmicrocrystalline cellulose microfibrils.

1) Preparation of the Systems Based on Cellulose Microfibrils and onCarboxymethylcellulose with a High Degree of Substitution:

The carboxymethylcellulose Blanose 12M8P® is dissolved in distilledwater.

The solution is then added to a suspension of Acticel 12® (ActiveOrganics) cellulose microfibrils and the mixture is stirred with anUltra-Turrax machine at 14,000 rpm for 5 min.

The amount of carboxymethylcellulose added is 15% by weight relative tothe weight of cellulose microfibrils and carboxymethylcellulose.

The mixture is then poured into crucibles, after which it is dried in anoven to a solids content of 97%, controlled by assaying the water by theKarl-Fischer method.

The dried mixture is then blended in a coffee mill, and then screenedthrough a 500 μm screen.

2) Redispersion of the Systems Based on Cellulose Microfibrils and onCarboxymethylcellulose with a High Degree of Substitution, andCharacterization:

The powder obtained is redispersed at 0.3% by weight of cellulosemicrofibrils in distilled water.

(a) Stirring is carried out using a deflocculating paddle at 1000 rpmfor 30 min.

Five minutes after stopping the stirring, a separation by settling takesplace in which the supernatant represents 91% of the volume.

(b) The stirring is carried out with an Ultra-Turrax machine at 14,000rpm for 5 min.

Five minutes after stopping the stirring, a separation by settling takesplace in which the supernatant represents 91% of the volume.

This example shows that there is no redispersion of the microfibrils,even when they are subjected to very high shear conditions.Consequently, contents of as low as 15% additive relative to themicrocrystalline microfibrils cannot be used to redisperse themicrofibrils after drying.

COMPARATIVE EXAMPLE 3

The aim of this example is to show the different behaviour ofmicrocrystalline cellulose microfibrils.

1) Preparation of the Systems Based on Cellulose Microfibrils and onXanthan Gum:

Comparative Example 2 is reproduced, except that the additive is xanthangum (Rhodopol 23®) and the amount is 30% by weight relative to theweight of cellulose microfibrils and xanthan gum.

2) Redispersion of the Systems Based on Cellulose Microfibrils and onXanthan Gum, and Characterization:

The powder obtained is redispersed at 0.3% by weight of cellulosemicrofibrils in distilled water.

(a) Stirring is carried out with a deflocculating paddle at 1000 rpm for30 min.

5 minutes after stopping the stirring, a separation by settling takesplace in which the supernatant represents 90% of the volume.

(b) The stirring is carried out with an Ultra-Turrax machine at 14,000rpm for 5 min.

5 minutes after stopping the stirring, a separation by settling takesplace in which the supernatant represents 90% of the volume.

This example shows that there is no redispersion of the microfibrils,even when they are subjected to very high shear conditions.Consequently, contents of about 30% additive relative to themicrocrystalline microfibrils cannot be used to redisperse themicrofibrils after drying.

EXAMPLE 4

1) Preparation of the Systems Based on Cellulose Nanofibrils and onCarboxymethylcellulose with a High Degree of Substitution:

The carboxymethylcellulose (degree of substitution equal to 1.2; ofmoderate viscosity—product Drilling Specialities Company—DrispacSuperlo) is dissolved in distilled water.

The solution is then added to the nanofibril stock dispersion (2.9% ofcellulose nanofibrils supplied by Générale Sucrière and prehomogenizedwith an Ultra-Turrax machine at 14,000 rpm (1 min per 100 g ofdispersion)) and the mixture is stirred with a deflocculating paddle at1000 rpm for 30 min.

The amount of carboxymethylcellulose added is from 15 to 30% by weightrelative to the weight of cellulose nanofibrils and ofcarboxymethylcellulose.

The mixture is then poured into crucibles, after which it is dried in aventilated oven at 40° C., to a solids content of 93%, which iscontrolled by assaying the water by the Karl-Fischer method.

The dried mixture is then blended in a coffee mill, after which it isscreened through a 500 μm screen.

2) Redispersion of the Systems Based on Cellulose Nanofibrils and onCarboxymethylcellulose with a High Degree of Substitution, andCharacterization:

The powder obtained is redispersed at 0.3% by weight of cellulosenanofibrils in distilled water. Stirring is carried out using adeflocculating paddle at 1000 rpm for 5 min or 30 min.

Flow rheology is carried out after 24 hours on an RFS 8400 rheometer inCouette geometry (scanning in shear gradient between 1 and 100 s⁻¹).

All the systems are compared with the non-dried cellulose nanofibrilsdiluted in water to 0.3% with an Ultra-Turrax machine at 14,000 rpm for1 min (optimum state of redispersion of the nanofibrils).

Table II shows the effect of the carboxymethylcellulose (DrispacSuperlo) concentration on the rheological profile of the cellulosenanofibrils after redispersion.

TABLE II Shear gradient Viscosity (Pa.s) (s⁻¹) Control Mixture 1 MixtureZ 1.27 4.1 × 10⁻¹ 5.6 × 10⁻¹ 2.9 × 10⁻¹ 2.01 2.6 × 10⁻¹ 4.2 × 10⁻¹ 1.9 ×10⁻¹ 5.05 1.3 × 10⁻¹ 2.5 × 10⁻¹ 1.1 × 10⁻¹ 12.7 1.0 × 10⁻¹ 1.5 × 10⁻¹7.3 × 10⁻² 20.1 6.0 × 10⁻² 1.2 × 10⁻¹ 5.4 × 10⁻² 50.5 2.8 × 10⁻² 7.2 ×10⁻² 3.5 × 10⁻² 80.0 2.5 × 10⁻² 5.7 × 10⁻² 2.7 × 10⁻²

Control: non-supplemented, non-dried cellulose nanofibrils obtained fromthe stock dispersion, and diluted with an Ultra-Turrax machine for oneminute at 14,000 rpm;

Mixture 1: 70% of nanofibrils and 30% of carboxymethylcellulose;redispersion with a deflocculating paddle at 1000 rpm for 5 min.

Mixture 2: 85% of nanofibrils and 15% of carboxymethylcellulose;redispersion with a deflocculating paddle at 1000 rpm for 30 min.

It should be noted that the suspensions obtained according to theinvention are stable over time.

It is moreover observed that the addition of carboxymethylcellulose witha high degree of substitution allows the redispersion of driednanofibrils and creates a state of dispersion of the nanofibrils suchthat, with 15% of additive, at least 72% of the viscosity of thenon-dried nanofibril suspension is recovered, at a shear gradient of 1s⁻¹, and with 30% of additive, at least 134% of the viscosity of thenon-dried suspension is recovered.

In addition, the rheological profile of shear-thinning type isconserved.

EXAMPLE 5

1) Preparation of the Systems Based on Cellulose Nanofibrils, onCarboxymethylcellulose and on Sucrose:

The carboxymethylcellulbse (degree of substitution equal to 1.2; ofmoderate viscosity—product Blanose 12M8P from Aqualon) is dissolved indistilled water.

The sucrose is also dissolved in distilled water.

The carboxymethylcellulose solution is then added to the nanofibrilstock dispersion (3.1% of cellulose nanofibrils supplied by Généralesucrière and prehomogenized with an Ultra-Turrax machine at 14,000 rpm—1min per 100 g of dispersion) and this mixture is stirred using adeflocculating paddle at 1000 rpm for 30 min.

In the case of the mixture without co-additive (mixture 1), the amountof carboxymethylcellulose added is 15% by weight relative to the weightof cellulose nanofibrils and carboxymethylcellulose. In the presence ofthe co-additive (mixture 2), the amount of carboxymethylcellulose addedis 10% by weight relative to the weight of cellulose nanofibrils and ofcarboxymethylcellulose and of co-additive.

The mixture is then poured into crucibles, after which it is dried in aventilated oven at 40° C., to a solids content of 96%, which iscontrolled by assaying the water by the Karl-Fischer method.

The dried mixture is then blended in a coffee mill, after which it isscreened through a 500 μm screen.

When the composition also comprises a co-additive. this is added to thestock dispersion at the same time as the additive.

The sucrose solution is then added to the nanofibril stock dispersionwhich has already been supplemented with carboxymethylcellulose, andthis mixture is stirred using a deflocculating paddle at 1000 rpm for 30min.

The amount of carboxymethylcellulose added is 10% and that of sucrose is20% by weight, relative to the weight of cellulose nanofibrils and ofcarboxymethylcellulose and of sucrose (mixture 2).

The mixture is then poured into crucibles, after which it is dried in aventilated oven at 40° C., to a solids content of 96%, which iscontrolled by assaying the water by the Karl-Fischer method.

2) Redispersion of the Systems Based on Cellulose Nanofibrils, onCarboxymethylcellulose and on Sucrose, and Characterization:

The powders obtained are redispersed at 0.3% by weight of cellulosenanofibrils in distilled water. Stirring is carried out using adeflocculating paddle at 1000 rpm for 30 min.

Flow rheology is carried out after 24 hours on an RFS 8400 rheometer inCouette geometry (scanning in shear gradient between 1 and 100 s⁻¹).

All the systems are compared with the control sample corresponding tothe non-dried cellulose nanofibrils with a solids content of 3.1%,diluted in water to 0.3% using a deflocculating paddle at 1000 rpm for 5min.

Mixture 1: 85% of nanofibrils and 15% of carboxymethylcellulose;redispersion using a deflocculating paddle at 1000 rpm for 30 min.

Mixture 2: 70% of nanofibrils, 10% of carboxymethylcellulose and 20% ofsucrose (co-additive); redispersion using a deflocculating paddle at1000 rpm for 30 min.

Table III shows the effect of the concentration ofcarboxymethylcellulose, as well as that of the co-additive, on therheological profile of the cellulose nanofibrils after redispersion.

TABLE III Shear gradient Viscosity (Pa.s) (s⁻¹) Control Mixture 1Mixture Z 1.27 × 10⁻¹ 2.0 4.3 × 10⁻¹ 2.7 2.01 × 10⁻¹ 1.2 3.4 × 10⁻¹ 1.55.05 × 10⁻¹ 2.8 × 10⁻¹ 2.4 × 10⁻¹ 5.3 × 10⁻¹ 1.27 9.7 × 10⁻² 1.1 × 10⁻¹2.5 × 10⁻¹ 2.01 6.2 × 10⁻² 7.4 × 10⁻² 1.8 × 10⁻¹ 5.05 3.5 × 10⁻² 4.0 ×10⁻² 7.8 × 10⁻¹ 12.7 2.7 × 10⁻² 2.6 × 10⁻² 4.6 × 10⁻² 20.1 1.9 × 10⁻²2.1 × 10⁻² 3.8 × 10⁻² 5.05 1.6 × 10⁻² 1.4 × 10⁻² 2.6 × 10⁻² 80.0 1.3 ×10⁻² 1.1 × 10⁻² 2.1 × 10⁻²

It should be noted that the suspensions obtained according to theinvention are stable over time.

It is observed that the addition of carboxymethylcellulose alone, with ahigh degree of substitution, allows the redispersion of driednanofibrils and makes it possible to create a state of dispersion of thenanofibrils such that, with 15% additive, at least 114% of the viscosityof the non-dried nanofibril suspension is recovered, for a sheargradient of greater than 1 s⁻¹, and at least 22% of the viscosity of thenon-dried suspension is recovered, for a shear gradient in the region of0.1 s⁻¹.

In the presence of co-additive, this recovery is 260% of the initialviscosity for a shear rate of greater than 1 s⁻¹, and 135% for a shearrate in the region of 0.1 s⁻¹. From these results, the partialreplacement of the carboxymethylcellulose with sucrose makes it possibleto increase the shear-thinning property of the nanofibrils.

EXAMPLE 6

1) Preparation of the Systems Based on Cellulose Nanofibrils and onXanthan Gum:

The xanthan gum (Rhodopol 23®) is dissolved in distilled water.

The solution is then added to the nanofibril stock solution (2.9% ofcellulose nanofibrils supplied by Générale sucrière and prehomogenizedusing an Ultra-Turrax machine at 14,000 rpm (1 min per 100 g ofdispersion)) and this mixture is stirred with a deflocculating paddle at1000 rpm for 30 min.

The amount of xanthan gum added is 30% by weight, relative to the weightof cellulose nanofibrils and xanthan gum.

The mixture is subsequently poured into crucibles and then dried in aventilated oven at 40° C., to a solids content of 97%, controlled byassaying the water by the Karl-Fischer method.

The dried mixture is then blended in a coffee mill, after which it isscreened through a 500 μm screen.

2) Redispersion of the Systems Based on Cellulose Nanofibrils and onXanthan Gum, and Characterization:

The powder obtained is redispersed at 0.3% by weight of cellulosenanofibrils in distilled water. Stirring is carried out using adeflocculating paddle at 1000 rpm for 30 min.

Flow rheology is carried out after 24 hours on an RFS 8400 rheometer inCouette geometry (scanning in shear gradient between 1 and 100 s⁻¹).

All the systems are compared with the non-dried cellulose nanofibrilsdiluted in water to 0.3% using an Ultra-Turrax machine at 14,000 rpm for1 min (optimum state of redispersion of the nanofibrils).

Table IV shows the effect of xanthan gum on the rheological profile ofthe cellulose nanofibrils after redispersion.

TABLE IV Shear gradient Viscosity (Pa.s) (s⁻¹) Control Mixture 1 1.274.1 × 10⁻¹ 10.0 × 10⁻¹  2.01 2.6 × 10⁻¹ 6.0 × 10⁻¹ 5.05 1.3 × 10⁻¹ 3.0 ×10⁻¹ 12.7 1.0 × 10⁻¹ 1.5 × 10⁻¹ 20.1 6.0 × 10⁻² 1.0 × 10⁻¹ 50.5 2.8 ×10⁻² 5.0 × 10⁻² 80.0 2.5 × 10⁻ 3.8 × 10⁻²

Control: Non-supplemented, non-dried cellulose nanofibrils, obtainedfrom the stock dispersion and diluted using an Ultra-Turrax machine for1 minute at 14,000 rpm:

Mixture 1: 70% of nanofibrils and 30% of xanthan gum; redispersion usinga deflocculating panel at 1000 rpm for 30 min.

It should be noted that the suspension obtained according to theinvention is stable over time.

It is moreover observed that the addition of xanthan gum allows theredispersion of dried nanofibrils and makes it possible to create astate of dispersion of the nanofibrils such that, with 30% additive, atleast 240% of the viscosity of the non-dried nanofibril suspension isrecovered, at a shear gradient of 1 s⁻¹.

In addition, the rheological profile of shear-thinning type is retained.

What is claimed is:
 1. A composition comprising amorphous cellulosenanofibrils, at least one additive which is carboxycellulose with adegree of substitution of more than 0.95, a natural polysaccharide, or apolyol and optionally at least one co-additive, the content of additiveand of optional co-additive being less than or equal to 30% by weightrelative to the weight of nanofibrils and of additive and of optionalco-additive.
 2. A composition according to claim 1, wherein thenanofibrils have a degree of crystallinity of less than or equal to 50%.3. A composition according to claim 1, wherein the nanofibrils have adegree of crystallinity of between 15% and 50%.
 4. A compositionaccording to claim 1, wherein the additive is carboxymethylcellulosewith a degree of substitution of more than 0.95.
 5. A compositionaccording to claim 1, wherein the additive is an anionic polysaccharide.6. A composition according to claim 5, wherein the polysaccharide isxanthan gum, succinoglycans, carrageenans and alginates.
 7. Acomposition according to claim 1, wherein the additive is a nonionicpolysaccharide.
 8. A composition according to claim 7, wherein thepolysaccharide is starch, nonionic derivatives of starch,galactomannans, and nonionic cellulose derivatives.
 9. A compositionaccording to claim 1, wherein the additive is a polyol.
 10. Acomposition according to claim 9, wherein the polyol is polyvinylalcohol.
 11. A composition according to claim 1, wherein the cellulosenanofibrils are obtained from cells consisting of at least about 80%primary walls.
 12. A composition according to claim 11, wherein thecellulose nanofibrils are charged with acids or with acidicpolysaccharides.
 13. A composition according to claim 1, wherein theco-additive is: carboxycellulose with a degree of substitution of lessthan or equal to 0.95, saccharide monomers or oligomers, compounds offormula (R¹R²N)COA, wherein R¹ and R², which may be identical ordifferent, represent hydrogen or a C₁-C₁₀ alkyl radical, A representshydrogen, a C₁-C₁₀ alkyl radical or alternatively a group R′¹R′²Nwherein R′¹ and R′², which may be identical or different, representhydrogen or a C₁-C₁₀ alkyl radical, cationic surfactants, or amphotericsurfactants.
 14. A composition according to claim 13, wherein theco-additive is saccharide monomers, saccharide oligomers,carboxycellulose with a degree of substitution less than or equal to0.95, or compounds of formula (R¹R²N)COA with a content of less than 30%by weight relative to the weight of nanofibrils and of additive andco-additive.
 15. A composition according to claim 13, wherein theco-additive is cationic or amphoteric surfactants with a content ofbetween 1 and 10% by weight relative to the weight of nanofibrils and ofadditive and of co-additive.
 16. A composition according to claim 1,wherein the co-additive content is less than 30% by weight relative tothe weight of nanofibrils and of additive and of co-additive.
 17. Acomposition according to claim 16, wherein the content of additive andof co-additive is between 5 and 25% by weight relative to the weight ofnanofibrils and of additive and of co-additive.
 18. A compositionaccording to claim 1, wherein the composition has a solids content of atleast 40% by weight.
 19. A suspension obtained by dispersing in water acompositon as defined in claim
 1. 20. A suspension according to claim19, having a level of viscosity corresponding to at least 50%, for ashear rate of at least 1 s⁻¹, of the level of viscosity of a cellulosenanofibril suspension which has not undergone a drying step and whichdoes not comprise an additive or co-additives.
 21. A cosmeticcomposition comprising a suspension as defined in claim
 19. 22. A foodformulation comprising a suspension as defined in claim
 19. 23. Aformulation for public works and construction comprising a suspension asdefined in claim
 19. 24. A cosmetic composition comprising a compositionas defined in claim
 1. 25. A food formulation comprising a compositionas defined in claim
 1. 26. A formulation for public works andconstruction comprising a composition as defined in claim
 1. 27. Aprocess for the preparation of a composition comprising amorphouscellulose nanofibrils, at least one additive which is carboxycellulosewith a degree of substitution of more than 0.95, a naturalpolysaccharide, or a polyol and optionally at least one co-additive, thecontent of additive and of optional co-additive being less than or equalto 30% by weight relative to the weight of nanofibrils and of additiveand of optional co-additive, wherein the cellulose nanofibrils areprepared from cellulosic pulp by carrying out at least one extraction,optionally at least one step of bleaching of the pulp thus treated, thenthe resulting pulp is separated out, and a homogenization step iscarried out in at least one cycle, wherein the following steps arecarried out: at least some of the additive and optionally co-additive(s)is added to the nanofibril suspension which has optionally undergone atleast one homogenization cycle, and a step of drying the suspension thussupplemented is carried out.
 28. A process according to claim 27,wherein at least some of the additive and optionally co-additive(s) areadded to the suspension after the homogenization step.
 29. A processaccording to claim 28, wherein at least some of the additive andoptionally co-additive(s) are added to the A suspension obtained fromthe homogenization step, after this suspension has undergone at leastone concentration step.
 30. A process according to either claim 29,wherein the concentration step is carried out in order to obtain asuspension with solids content of not more than about 35% by weight. 31.A process according to claim 28, wherein at least some of the additiveand optionally co-additive(s) are added to the suspension after thehomogenization step, before the said A suspension has undergone aconcentration step.
 32. A process according to either claim 31, whereinthe concentration step is carried out in order to obtain a suspensionwith solids content of not more than about 35% by weight.
 33. A processaccording to claim 28, wherein at least some of the additive andoptionally co-additive(s) are added to the suspension before or duringthe homogenization step.
 34. A process according to claim 27, whereinthe cellulose nanofibril suspension is shaped prior to drying.
 35. Aprocess according to claim 27, wherein the drying step is carried out soas to maintain not less than 5% by weight of water relative to theweight of cellulose nanofibrils.
 36. A process according to claim 35,wherein a blending step is carried out after the drying step.